At present, there is no way for a hint provider to return distinct hints
for different resource types via a call to GetTopologyHints(). This
means that hint providers that govern multiple resource types (e.g. the
devicemanager) must do some sort of "pre-merge" on the hints it
generates for each resource type before passing them back to the
TopologyManager.
This patch changes the GetTopologyHints() interface to allow a hint
provider to pass back raw hints for each resource type, and allow the
TopologyManager to merge them using a single unified strategy.
This change also allows the TopologyManager to recognize which
resource type a set of hints originated from, should this information
become useful in the future.
